Portland, Oregon

Columbia
Boulevard Wastewater Treatment Plant (CBWTP), the
largest wastewater plant in Oregon, is operated by
the Portland Bureau of Environmental Services (BES).
The facility is the collection point for about 1,800
miles of wastewater sewer pipes and includes 92
pumping stations. CBWTP treats 80-90 million gallons
of sewage and wastewater each day. CBWTP’s
wastewater treatment process produces about one
million cubic feet of anaerobic digester gas each
day and about 55 percent of the gas is methane.
Typically, treatment plants like CBWTP flare or burn
excess biogas. Using this fuel source to generate
power provides the facility with a free, renewable
energy source that displaces local utility
electricity (likely generated from natural gas or
coal fuels).

The
plant has investigated several technologies over the
years to reclaim this “biogas” for electrical power
generation to reduce utility costs and has installed
a number of these advanced systems. CBWTP installed
a 200 kW anaerobic digester gas fuel cell power
generation project in 1999, but it was
decommissioned in 2005. In April 2003 four 30kW
Capstone microturbines were installed. Based
on its experience re-claiming biogas for electricity
generation with other CHP technologies, the City
(with assistance from Oregon state renewable
incentive funding) made a major CHP investment in
June 2008 installing two 850kW I/C Engine-Generators
which are operating successfully and have
substantially reduced the need to flare biogas.